While at Yale, he was active in the Yale Political Union, helped organize the Army ROTC company for the southern tier of Connecticut and served as its first cadet commander, and spent a month-long rotation with the 1-15th Field Artillery at Camp Hovey, South Korea. He earned the designation of Distinguished Military Graduate for his academic and military performance and was the top-ranked Cadet in the state.[4]

Upon returning to Fort Bragg, he transferred to the 4-73 Cavalry (Reconnaissance, Surveillance, & Target Acquisition) of the 82nd Airborne Division, deploying to the Farah Province of Afghanistan as a Platoon Leader. He spent a year in Afghanistan in support of Operation Enduring Freedom from August 2009 to August 2010, including the areas of Bala Murghab and Bala Buluk. Towards the end of the deployment, he was promoted to Squadron Senior Logistics Officer (S4) and earned the rank of captain. During his military service, he earned 17 awards and decorations:[3]

After leaving the Army, Day returned to Rockland County, earned an MBA from Columbia Business School in 2013 and began working in private equity & venture capital at Selway Capital, where he is currently a Vice President.[6]

Day faced a substantial deficit in party registration and was defeated by Nita Lowey in the 2014 general election by a margin of 54 percent to 46 percent. This was Lowey's smallest margin of victory since taking office.[11][12] Lowey outspent Day by a 10:1 margin in the campaign.[13][14][15]

Chris Day declared his candidacy for Supervisor of Orangetown, New York in January 2017.[16] After all the ballots were counted, Day won the election by a close margin of 163 votes out of 16,189 votes cast, or 50.5% to 49.5%.[17]

Day was sworn into office on January 3, 2018, five days after his 33rd birthday.[18]